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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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Quick Links

09/13/19

Message Overview:

Fault Message:

APU LOW OIL PRESSURE

Fault Code:

4960130APU

Associated CAS:

APU OIL LO PRESS
(Caution)

APU SHUTDOWN
(Advisory)

Reporting LRU: Full-Authority Digital Engine-Controller (FADEC) System
System Description: 49-90-00
Schematic Diagram: 49-90-00 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wiring Diagram: 49-12-01 [ Global Express ]  [ G5000 ]  [ Global XRS ]
49-61-01 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Fault Description:

This Engine Indication and Crew Alerting System (EICAS) message shows when the Low Oil Pressure Switch reads a low oil pressure for 15 seconds. This occurs after the Auxiliary Power Unit (APU) is ready-to-load and the aircraft is in flight.

During ground operation only, the APU will be automatically shut-down, followed by the CAS advisory message 'APU SHUTDOWN'.

Troubleshooting Tips:

  • Low Oil Pressure Switch (S1)
  • Auxiliary Power Unit (APU) Full-Authority Digital Engine-Controller (FADEC) (A108)
  • Oil Pump (B27)
  • Auxiliary Power Unit (APU) Gearbox
  • Auxiliary Power Unit (APU) (AP7)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Switch is closed 30psig.

During ground operation only, if the oil pressure decreases below 30 psig, the LOP switch contacts close, first turning on the amber CAS message reading APU OIL LO PRESS. Next, after a time delay of 15 seconds, the APU will be shutdown, followed by the CAS advisory message APU SHUTDOWN.

If in flight, with the same condition, the APU would keep operating with a CAS message APU OIL LO PRESS (Caution).

During the "APU IN BITE" checks the LOP switch is checked by the FADEC. On the ground, if the switch is electrically open (>30 psig), APU starts are inhibited by the FADEC. With the same condition, but this time the switch is electrically closed (<30 psig), APU would start. At 95% rpm + oil press less than 30 psig + 15 seconds, the APU would shutdown with an APU SHUTDOWN (Advisory) message.

If the prestart BITE detects a defective LOP switch on the ground NO CAS message will be displayed, but if in flight you would get "APU FAULT" (Advisory) message.

Quick Links:

Quantity Check of the Oil Supply in the APU AMM 12-14-09-610-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Servicing of the APU Oil Supply AMM 12-14-09-612-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the APU AMM 49-10-00-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the APU AMM 49-10-00-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the Full-Authority Digital Engine-Controller (FADEC) AMM 49-61-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Full-Authority Digital Engine-Controller (FADEC) AMM 49-61-01-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the Oil Pump AMM 49-90-21-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Oil Pump AMM 49-90-21-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the Low Oil-Pressure Switch AMM 49-90-41-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Low Oil-Pressure Switch AMM 49-90-41-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. Inspect for oil leaks around the auxiliary power unit (APU) access doors before you open them and also in and around the APU exhaust duct (on the right side of the aircraft tail).
  2. Inspect the low oil pressure switch, the oil pump, the gearbox, the APU, the electrical harness, and APU exhaust (inside APU enclosure) for signs of oil leaks and damage.

    1. If damages are found, repair as required and do close out.
    2. If damages are not found, continue with next step.

  3. Visually check the oil quantity in the APU (if APU oil level was low, investigate absence of APU OIL LOW QTY message).

    1. If oil quality is not good, change oil and continue with next step.
    2. If oil quality is good, continue with next step.

  4. Perform wiring checks between APU FADEC (A108) and the low oil pressure switch (S1P1) as follow:

    From To Result
    A108AP1-J4 A108AP1-E5

    1. If wiring checks are not good, repair defective wiring as required and do close out.
    2. If wiring checks are good, continue with next step.

  5. Inspect APU FADEC rack, pins, and sockets for damage, or FOD.

    1. If damages are found, repair as required and do close out.
    2. If damages are not found, continue with next step.

  6. Re-rack FADEC, verify if fault is still present.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

  7. Swap the low oil pressure switch.

    1. If system checks are good, replace defective low oil pressure switch and do close out.
    2. If fault remains, continue with next step.

  8. Swap the APU FADECs.

    1. If system checks are good, replace defective APU FADEC and do close out.
    2. If fault remains, continue with next step.

  9. Swap the oil pump.

    1. If system checks are good, defective oil pump and do close out.
    2. If fault remains, continue with next step.

  10. Replace APU.
  11. Do close out.

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